Q8 = dctmtx(8)
A = orth(Q8)
E = norm(eye(8)-Q8'*Q8,'fro')
e8 = eig(Q8)
[V,D] = eig(Q8)

Q4 = dctmtx(4)
A4 = orth(Q4)
E4 = norm(eye(4)-Q4'*Q4,'fro')